This application claims the priority of German Patent Application Serial No. 199 58 834, filed Nov. 29, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates to an apparatus for grasping a load from above or from the side, in particular for use in a manipulator.
It is generally known to provide a gripping apparatus for grasping loads with two confronting gripper jaws which normally are arranged underneath across an elongate beam. The gripper jaws are hereby movable in opposition to one another and mounted to the elongate beam, whereby both gripper jaws may be movably arranged, or one of the gripper jaws may be fixed in place through securement to the elongate beam. There are also proposals to guide the gripper jaws on two parallel elongate beams to enhance the absorption of lateral forces.
Common to all conventional gripping apparatuses is their lack of a compact structure which would enable the use of a gripping apparatus, especially for use in a manipulator, in narrow containers for picking up workpieces or the like while yet applying a greatest possible gripping stroke.
It is thus an object of the present invention to provide an improved apparatus for grasping loads, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved apparatus for grasping loads from above or from the side, especially for use in a manipulator while yet applying a greatest possible gripping stroke even in narrow and tight openings.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a pair of elongate beams in parallel relationship, a pair of carriers, extending in a direction of the elongate beams and disposed in spaced-apart relationship, when viewed in a longitudinal direction of the carriers, each of the carriers supported by a corresponding one of the elongate beams and guided for displacement longitudinally in the direction of the elongate beams relative to the other one of the carriers at least over a portion of a length of the carriers, a pair of confronting grippers mounted respectively to ends of the carriers above or below the elongate beams and positioned on the outside of the carriers, when viewed transversely to the carriers and when the carriers are completely moved apart; and a primary fluid-operated system for moving the carriers in opposition to one another.
In this manner, the gripping apparatus according to the present invention has a very compact configuration.
Suitably, both elongate beams are configured as profiled rails to attain a precise guidance of the carriers while sufficiently absorbing transverse forces. The guidance of the elongate beams can be further improved when each carrier is mounted to a runner which at least partially embraces the profiled rail and engages the profile of the profiled rail.
According to another feature of the present invention, each of the running elements has a U-shaped configuration and includes balls circulating in the running element for support upon a corresponding one of the profiled rails. This configuration is effective in particular for absorption of transverse forces.
According to another feature of the present invention, the elongate beams and the carriers are fitted in a housing, whereby each of the carriers has a first attachment which projects out of the housing for securement to a corresponding one of the grippers. Suitably, each of the grippers is configured as a plate-shaped clamping jaw.
According to another feature of the present invention, the primary fluid-operated system includes two fluid-operated mechanisms supported on opposite sides of the housing and operatively connected to the carriers in one-to-one correspondence, with each of the fluid-operated mechanisms including a pneumatic cylinder and a piston rod moveable in and out of the pneumatic cylinder. Such a configuration results in a compact structure while realizing high grasping or clamping forces. Suitably, whereas each pneumatic cylinder is secured to the housing, the piston rods are secured to a second attachment of the carriers. To further enhance the compactness of the gripping apparatus according to the present invention, the first and second attachments are disposed on different ends of the carriers and face away from one another.
In order to accomplish a synchronization of a movement of the carriers, the gripping apparatus according to the present invention has a synchronizing mechanism which includes a pair of racks disposed in parallel relationship to the elongate beams and respectively mounted to one end of the second attachment of the carriers, and a pinion disposed between and in mesh with the racks. Thus, the movement of the racks in opposition to one another is synchronized.
According to another feature of the present invention, the gripping apparatus is equipped with an emergency holding mechanism that allows the grippers to maintain their grasping position, when a pressure drop in the primary fluid-operated system and a resultant decrease of a clamping force during load transport are encountered. The emergency holding mechanism includes a pair of multiple-plate assemblies, with each of the multiple-plate assemblies including a first set of flat plates spaced equally from one another in parallel relationship to the elongate beams and securely fixed to a free end of a corresponding one of the second attachments of the carriers, a second set of flat plates securely fixed to one end of the housing, whereby the plates of the first and second sets of flat plates bear laterally upon one another, and an adjuster compressing the plates of the first and second sets of plates from the side, when encountering a pressure drop of the primary fluid-operated system and a resultant decrease of the clamping force exerted by the grippers. The adjuster of each multiple-plate assembly provides a forced engagement between the plates so that the grippers are prevented from moving apart even when a pressure drop is encountered in the primary fluid-operated system.
The adjuster may be configured as a swingable double-arm lever, having one end acted upon by a spring force, and another end acted upon by a counterforce in correspondence to the pressure applied by the pneumatic cylinder of the primary fluid-operated system, so that the adjuster presses against the plates at a force which corresponds to a difference of the spring force and the counterforce. The counterforce may be implemented by a secondary fluid-operated system which includes for each multiple-plate assembly a pneumatic auxiliary cylinder and a piston rod moveable in and out with respect to the pneumatic auxiliary cylinder, with the piston rod acting upon the other end of the double-arm lever. Suitably, a single pressure source is used for supply of fluid to the pneumatic auxiliary cylinders of the secondary fluid-operated system and the pneumatic cylinders of the primary fluid-operated system.
According to another feature of the present invention, the double-arm lever is configured as a triangular plate, with two neighboring corners defining the one end of the lever and the other end of the lever, and a third corner of the lever defining the adjuster. The third corner juts hereby out from the double-arm lever as a lobe and is pressed against the plates when the double-arm lever swings.
Suitably, the triangular plate defines a center and is rotatable about the center to thereby realize favorable lever proportions.
According to another feature of the present invention, the housing is made of two housing parts which are open on one end and fit within one another at a formation of a gap-like free space, with spacer elements received in the free space for interconnecting the housing parts.